Nolina microcarpa S. Watson (Asparagaceae) shrubs in northwest Arizona were covered with insect-emergence traps to determine whether Triarius trivittatus Horn (Coleoptera: Chrysomelidae), a beetle species that carries pollen from male to female flowers, undergoes larval development on the plant. The 3 traps covered different clumps of leaf rosettes and caught 39 beetles, 15 males and 24 females, during 27 May–24 June 2019. Larvae of T. trivittatus likely develop on roots, similar to other beetles in the same tribe, or on underground stems that connect leaf rosettes. Development of larvae on the plant, as well as pollen transport to female flowers by the adult beetles, suggests that N. microcarpa and T. trivittatus have a mutualistic relationship.